Built to inform

Tunnel vision – tunnelling special

Last June, the Prime Minister inaugurated India’s longest transportation passage, an 11km long tunnel across the treacherous Pir Panjal mountain range on the Banihal-Qazigund railway line in Jammu & Kashmir. The tunnel has been constructed using New Austrian Tunnelling Method (NATM) and it is for the first time such a method has been used on such a large scale in India.
It was some four decades ago that India opened up a new sector in infrastructure development, tunnelling. Prior to that, it was largely confined to hydro power projects, irrigation and urban water supply and sewage management.
Today, tunnelling projects have completely changed to accommodate urban transportation systems and road connectivity in mountainous regions. Moreover, tunnelling is no more an exclusive domain of the government sector, with MNC firms, both in tunnel construction and consultancy, actively participating in government-sponsored and private sector projects in the country.
In recent times, the government has been encouraging cities with population more than three million to develop mass transit system. Popular among them has been the metro rail that has been proposed in nearly two dozen cities with actual construction on in around nine cities. With more cities mulling the idea of constructing metro rail, there’s an opportunity for all the stakeholders. The metro rail provides an efficient public transport system which is environment friendly too. Considering that most metros are congested and are badly in need of further infrastructure development, it does imply that tunnelling will be a part of such projects. Not to mention that the increasing populace is also seeing development of water supply and sewerage tunnels being built.
These developments, says a spokesperson at Frost & Sullivan, are attracting talent from several international players who are specialised in tunnel designing, equipment hiring, tunnelling and maintenance works.
"The scope for tunnelling business in urban infrastructure and transportation is enormous in India. The Indian Railways wants to tunnel for close to 100km in the Himalayas, particularly in Kashmir to reduce the travel distance.
The Bengaluru Metro expansion and Chennai Metro have significant tunnelling components. So naturally, India is an attractive market for international players in the sector," he adds.
Tunnels provide uninterrupted mode of transport in regions that get heavy snow fall. They shorten the distance from one point to another instead of going over or around a hill or a mountain.
In case of water distribution in cities, underground tunnels provide safe and long lasting solutions as there is no pilferage and almost zero maintenance cost.
Tunnels reduce noise, air pollution, and are not visually unattractive as surface roads. If only the capital costs of construction are used to compare alternative transportation routes, then tunnelling would never become a viable option. However, the intangible costs, such as effect on community health, air pollution and noise, make tunnelling viable if they are assessed.
Speaking about some of the techniques used in conducting round investigations, a must for tunnelling projects, Uday Vartak, chief technical officer, CEC International Corporation India (CICI) says, “Extensive geo-technical investigations are conducted prior to sending out tenders. It is necessary to evaluate the properties of the soil and rock samples in terms of their strength, abrasion index, water table, etc. collected during geo-technical investigation. In spite of the best efforts during the investigations, surprises while excavating tunnels cannot be ruled out.”
This can be nullified with an equitable contract clause and timely redressal of issues particularly related to unforeseen geological conditions. The study done by clients generally is not extensive and dates are not analysed in details by stakeholders due to inadequate time available for bidding.
Kapil Bhati, managing director, Robbins Tunnelling & Trenchless Technology, says, “Some of the techniques used in the initial ground investigations are geological/seismic survey, satellite mapping of the project and core samples.
Difficult terrain or approach to the site, high cover of the tunnel to take core samples is issues that affect the proper and realistic investigations. Use of advance equipment/techniques for the survey can help to overcome the challenges in this area.”
Vartak of CICI says, “Feasibility, shifting of utilities, traffic density, high capital expenditure, safety and long gestation period are critical factors which need detailing for individual projects. Underground metro projects are more equipment intensive and on a thumb rule are 2.5 times costlier than elevated corridors. A rational mix of elevated and underground portion keeping in mind the local geographical conditions is important.”
In terms of methods of tunnel construction, most of the projects in India have been drill and blast, NATM, cut and cover and mechanised tunnelling by tunnel boring machines. Last one decade, mechanised tunnelling has become prevalent due to its various advantages over other tunnelling methods.
However, most companies are surprised that despite a large number of tunnelling projects taking place in India and more expected to happen, no major equipment manufacturer has shifted base to India. Purnachandra Bhave, general manager (EPC), Hindustan Construction Company, says, “A majority of development in complex tunnelling equipment still remains the forte of Scandinavian countries such as Sweden and Norway. However, few vendors have set up shop to provide fabricated components. India still lags on metallurgy issues in drilling equipment and component life is a concern.”
In terms of technology, Japan has made considerable advances in the tunnel boring machine. However, they have not shared it with the rest of the world.
If they share their know-how, more advancement in the tunnelling technology can be achieved.
As regards to construction chemicals used in the tunnelling application, India is at par with global standards and the applications that are typically used in the soil and water treatment, ingress control, etc are available here.
Despite this, there is room for improvements in terms of technology, regulations, equipment, etc. that will ensure best practices. Bhati says that assessment of proper site investigation helps the owner to decide proper equipment/ contractor and methodology. Once this is defined, the equipment can be proposed which can have all the modern technology to handle difficult ground/projects.
For example, in order to handle complex geology of the tunnel consisting of hard rock, soft soil and mixed face. For such complex geology tunnel a dual mode hybrid hard rock EPB machine can be suggested which can handle all complex geology and complete the job in time. Or an open gripper main beam tunnel boring machine implementation of McNally system can be provided to handle poor/ loose rock strata and provide ground support required for consistent advancement of excavation.
Vartak says, “It is important to ensure that best practices are a part of tender documents and will be implemented in letter and spirit. Unforeseen ground conditions pose huge risk to owner as well as contractor. The risk must be allocated appropriately. There has to be a band of variation beyond that risk cannot be absorbed by contractor. The owner should share it otherwise.”
In terms of contracting practices, it is a general consensus among contractors that majority of the underground tunnel boring works are invited on the design and build mode and involves funding by external sources like Japan International Cooperation Agency (JICA), Asian Development Bank, etc. Procurement guidelines of these agencies are adopted by the clients. Block design parameters should be more precise to enable EPC contractors a proper evaluation at the tender stage. Extensive geotechnical investigation if conducted prior to the invitation of the tenders would only enable least variations/disputes during execution.
Bhati says that the most common contracting practice followed in India is International Federation of Consulting Engineers (FIDIC).
He points out tosome major key issues:
• Deficiencies in tender/contract documents:
In many cases clauses are included in documents related to physical realties of the work that are not based on sound logic. These shortcomings lead to dispute between the owner and contractor and ultimate stalemate or inordinate delays in the work.
• The lack of a system for establishing accountability for delays and resulting cost overruns is another deficiency.
• Improper contract documents and management during project execution increase the burden of claims.
• Sometimes all necessary clearances are lacking such as site investigation details, financing, project cost estimate, and unclear designs.
• Mutual trust between the owner and contractor is must to settle any/all issues between the parties. Implementation of clauses that can cover the issues of the contractor for delays/ faults not attributable to them in the contract document is essential.
Logical, timely intervention and taking decision by the appropriate authorities is vital in timely and within budget completion of any project.